I speculate that as melt progresses towards the north pole in the years to come, freeze onset dates might actually become slightly earlier rather than later.
The following chart shows the dates for IJIS extent minima. In general there seems to be no trend. More accuracy can be achieved by averaging around the minimum to avoid noise.
Oren, I realise that, in any given year, a polyna at higher latitude is likely to commence its autumnal refreeze at an earlier date than an equivalent polyna at a lower latitude. I can therefore see how one might expect that the gradual pole-ward retreat of peripheral ice, might indicate that refreezing could commence earlier.
This viewpoint, however, might fail to fully incorporate the ice/albedo positive feedback mechanism, which, as you know, results in greater heat storage within the body of the ocean. It is this cumulative build up in the heat content which would serve to delay refreeze.
During the period since I posted a link to that NASA article, I managed to find the paper I had mentally misplaced. (
Something which is happening with alarming frequency as the years go by.)
The lead author was Julienne Stroeve - a name I'm certain you recognise - and here is an open access link to the AGU's Geophysical Research Letters article...
http://onlinelibrary.wiley.com/doi/10.1002/2013GL058951/fullAnother related paper would be this one, which has Walt Meier as the lead author...
http://onlinelibrary.wiley.com/doi/10.1002/2013RG000431/fullIn either article, doing a simple search on the term "delay" gets one quickly to the relevant sections.
However, you are completely correct in pointing out that there are significant differences when one looks at regions, rather than the Arctic as a whole. Quoting from Para 3.3 (Relationship Between Autumn Freezeup and Sea Surface Temperatures) in the Stroeve paper...
"While this is representative of the Arctic as a whole, there are regional differences. In the Chukchi, Beaufort, E. Siberian, Laptev, Kara, and Barents seas, the observed freezeup delay falls within the estimated value (Table S3), suggesting the delay in autumn freezeup is largely driven by the observed increases in SSTs in these regions. These SST increases, together with recent trends toward warmer air temperatures in September (Figure S8), result in a small difference in the air-ocean temperature difference, limiting the amount of latent heat released and a delay in sea ice formation.
Regions outside of the Arctic basin do not appear to show this same relationship however (i.e., Sea of Okhotsk, Bering, Hudson, and Baffin Bay, E. Greenland Sea). Instead large discrepancies between the observed changes in autumn freezeup and that estimated based on the change in SSTs are found, with the actual freezeup occurring between 1 week and 1 month earlier than estimated by equation (3). All these regions, except for Hudson Bay show earlier freezeup in 2000–2012 compared with that in 1982–1999, while SSTs have generally warmed. Trends toward cooler September air temperatures (Figure S8) in these regions may partly explain this discrepancy. While trends are toward warmer SSTs and higher OHC, the air-ocean temperature difference is becoming larger, allowing for the sea surface to release latent heat at a faster rate and for sublimation of sea ice to occur sooner. Ocean dynamics could also be playing an important role in the amount of sea ice found, particularly in the E. Greenland Sea.
In summary, while these preliminary results look promising, a need remains for more extensive research and better understanding of the processes affecting freezeup on a regional scale."